The present invention relates to an electrode for a lead-acid storage cell. Such an electrode includes an active material contained in a support together with current collectors. In the case of grid type plates, the grid is made of lead or of a lead alloy and is used simultaneously as a support and as a current collector; however, the electrode may also include extra current collectors outside the grid proper which serve to connect it to neighbouring electrodes or to a terminal electrode.
In the case of tube type plates, the active material is contained in sleeves, and the current collectors are constituted in particular by spines inserted in the sleeves and connected to a frame; the spine/frame assembly is made of lead or of a lead alloy and can be connected to current collectors outside the frame as in the case of grid type plates.
In all cases, and for either positive or negative electrodes, it is necessary to increase the electric conductivity of the current collectors as much as possible, whether or not they are in contact with the active material.
Therefore, current collectors have already been used which are made of a material whose electric conductivity is higher than that of lead, e.g. copper or aluminum; to this end said collectors have also been covered with a protective layer made of iron, lead-tin alloy, etc.
However, during operation, the positive electrodes of lead-acid storage cells undergo extensive corrosion; for example, in the case of grid-type plates, following an accidental defect in the moulding of the grid, or simply at the end of the storage cell's life, it can happen that sulphuric acid enters the core of the grid. If the grid is made of a copper or aluminum conductor coated with known substances, this very rapidly destroys the conductor completely. If copper is used, it migrates towards the negative electrode and causes rapid self-discharge of the storage cell.
Preferred embodiments of the present invention mitigate these drawbacks.